Metallic burner tiles

ABSTRACT

The present disclosure seeks to provide a metallic burner tile for use in industrial processes such as cracking. The tile is substantially metallic (e.g. more than 80%) with the balance being ceramic coating on surfaces exposed to high temperature. The tile is lighter and more durable than the current ceramic burners.

FIELD

The present disclosure relates to the field of burners for industrialapplications particularly applications at temperatures greater than 800°C. such as petrochemicals processing including cracking of paraffins. Insome embodiments the present disclosure relates to metallic floor orwall burners used in such applications.

BACKGROUND

The cracking of paraffins such as ethane to olefins such as ethylene isenergy intensive. The paraffin passes through tubes or coils in afurnace with flue gasses heated up to about 1200° C. The internal wallsof the furnace are refractory material which radiates heat to theprocess coils. The walls are heated by a series of burners in the flooror walls or both. The temperature of the walls may reach temperature inthe range from 700° C. to 1350° C., or from 800° C. to 1200° C.

Currently, parts of the burner in the interior of the furnace aremanufactured with a refractory material. This makes the burners heavy.Additionally, the refractory or ceramic tends to be brittle and canbreak during transport and operation.

British patent 1,480,150 discloses an improvement relating to hightemperature burners in which a metallic quarl having an inner and outersurface and providing a closed chamber surrounds the burner. A coolingmedium passes through the quarl to keep the burner at a lowertemperature. The patents teaches the cooling medium could be air beingfed to the burner or exhaust gasses from combustion. The referenceteaches away from the present disclosure as a double walled quarl is notused.

The paper Development of Ultra Compact Low NOx Burner for HeatingFurnace in the Proceedings of the 1998 International Gas ResearchConference by A. Omori of Osaka Gas Co., Ltd. pages 269-276 discloses ametal burner. The burner does not have channels in the interior metalburner walls to pass air over the wall and cool the burner. Further theburner is designed to provide a vortex flow of air to the flame toincrease the surface area and reducing the flame temperature. Such areduction in flame temperature may not be desirable.

United States Patent application 20100021853 published Jan. 28, 2010 inthe name of Bussman assigned to John Zink Company LLC. Teaches a burnerto produce low NOx emissions. In the figures the burners are tiles (e.g.ceramic or refractory) in which a significant amount of the burner ismade of such materials. In contrast the burners disclosed hereincomprise less than 20 wt % of ceramic or refractory, or for example, noceramic or refractory. Additionally, if ceramic or refractory is used itis over coated on the outside of the metal.

The present disclosure seeks to provide a metallic, or substantiallymetallic burner for use in industrial applications such as crackerfurnaces.

SUMMARY

The present disclosure provides a substantially metallic burner having aservice temperature of not less than about 1200° C. for a crackingfurnace operating with walls at temperatures from 700° C. to 1350° C.comprising:

i) a substantially metallic flow passage defined by at least one surfacehaving a downstream outlet and at least one upstream inlet for at leasta gaseous oxidant;

ii) said substantially metallic flow passage having at least one baffledirecting the flow of oxidant and fuel against the internal surface ofthe burner facing the furnace; and

ii) optionally one or more arrays of heat convective surfaces selectedfrom baffles, ribs, fins and protuberances to direct the flow of said atleast a gaseous oxidant over said one or more arrays on the internalsurface of said substantially metallic flow passage.

In a further embodiment there is provided a burner having an arrays ofheat convective surfaces that are ribs that define at least onecontinuous series of parallel channels at least on the internal surfaceof the portions of the burner exposed to the cracking furnace.

In a further embodiment there is provided a burner wherein the channelshave a height to width ratio from 0.1 to 2, or from 0.25 to 2, in someembodiments from 0.5 to 2, in further embodiments from 0.5 to 1.

In a further embodiment there is provided a burner, wherein one or moremetallic fuel line terminate(s) proximate the external front surface forsaid flow passage from 25 to 75% of the height of the front of the flowpassage.

In a further embodiment there is provided a burner wherein said at leastone metallic surface has a thickness from 4 to 25 mm

In a further embodiment there is provided a burner comprising incooperating arrangement:

i) a lower metal flow passage for one or more gaseous oxidants having anopen back end, closed side walls and a closed bottom wall, a front walland a top wall which does not extent the full length of the side wallsto define an open upward facing vent in the upper front end of the flowpassage; and a metal front wall continuous with the bottom wall of theflow passage;

ii) a metal upper section having the same width as the metal flowpassage comprising a front wall, two parallel side walls and a rear walldefining a chamber, an open bottom which co-operates with the open ventin the flow passage and a front wall and an open top said front wall andback wall having openings therein at substantially the same height andlateral displacement to provide for one or more fuel supply linespassing from the back to the front of said upper section;

iii) either:

-   -   a) one or more metal, or ceramic coated metal, top plates        cooperating with the open top of the upper metal section, said        one or more top plates having a planar surface optionally having        a curved leading edge and one or more substantially circular        passageways there through, said back section having one or more        outlets which may be circular, oval, or polygon (e.g.        triangular, rectangular or square) for said one or more gaseous        oxidant there through; or    -   b) a continuation of the upper front wall extending to the back        wall of the upper section said continuation having a leading        edge optionally curved and optionally having one or more        substantially circular passageways there through, and a planar        back section having one or more outlets which may be circular,        oval, or polygon (e.g. triangular, rectangular or square) for        said one or more gaseous oxidants there through, said back        section optionally being coated with a ceramic; and

iv) one or more descending baffle extending into said metal uppersection.

As used herein planar refers to the degree of curvature of an element.But the current disclosure is not limited by the shape or geometry ofthe sides of the enclosure (e.g. box). While planar surfaces areexemplified, embodiments where the sides of the enclosure are curved orwavy are also envisioned.

In a further embodiment there is provided a burner wherein there is adescending baffle depending from a region not more than 10% forward ofthe forward lip of said one or more outlets for at least a gaseousoxidant, to the forward lip of said one or more outlets for said one ormore gaseous oxidants, said baffle descending inside the upper metalsection of the burner from 50 to 90% of the height of the front face ofsaid burner; and extending laterally across the inner surface of theburner from 100 to 75% of the width of the face of said burner, saiddescending baffle being positioned so that there are substantially equalopenings on each side of the descending baffle relative to the sidewalls of the metal upper section and where necessary said descendingbaffle having one or more circular channels there through to permit oneor more fuel supply lines to pass there through.

In a further embodiment there is provided a burner having series ofparallel longitudinal internal ribs to direct the flow of said at leasta gaseous oxidant over the forward facing surface of said descendingbaffle.

In a further embodiment there is provided a burner further comprising anascending baffle extending forward from the upper wall of said lowermetal flow passage into from 45 to 85% of the open area in the chamberof a metal upper section.

In a further embodiment there is provided a burner wherein saidascending baffle extending forward from the upper wall of said lowermetal flow passage is bent in its forward section up towards the opentop to provide an upwards facing ascending baffle parallel to the innerfront wall of upper section and where required the upward extendingsection of said ascending baffle having one or more circular channelsthere through to permit one or more fuel supply lines to pass therethrough.

In a further embodiment there is provided a burner wherein saidascending baffle extending forward from the upper wall of said lowermetal flow passage further comprises on the surface facing the innerfront wall of upper section a series of parallel longitudinal internalribs to direct the flow of said at least a gaseous oxidant over theinternal surface of said substantially metallic flow passage.

In a further embodiment there is provided a burner wherein the channelshave a height to width ratio from 0.1 to 2. In some embodiments the ribsmay have a height from 4 to 25 mm, or from 8 to 22 mm, in some instancesfrom 10 to 20 mm.

In a further embodiment there is provided a burner wherein there is anascending baffle extending forward from the upper wall of said lowermetal flow passage into from 45 to 85% of the open area in the chamberof a metal upper section.

In a further embodiment there is provided a burner wherein saidascending baffle extending forward from the upper wall of said lowermetal flow passage is bent in its forward section up towards said one ormore outlets to provide an upwards facing ascending baffle parallel tothe inner front wall of upper section and where required the upwardextending section of said ascending baffle having one or more circularchannels there through to permit one or more fuel supply lines to passthere through.

In a further embodiment there is provided a burner wherein saidascending baffle extending forward from the upper wall of said lowermetal flow passage further comprises on the surface facing the innerfront wall of upper section a series of parallel longitudinal internalribs to direct the flow of said at least a gaseous oxidant over theinternal surface of said substantially metallic flow passage.

In a further embodiment there is provided a burner wherein the channelshave a height to width ratio from 0.1 to 2.

In a further embodiment there is provided a burner wherein said one ormore top plates is present and is metal.

In a further embodiment there is provided a burner said one or more topplates is present and is metal coated with ceramic.

In a further embodiment there is provided a burner wherein the upperfront wall continues to the upper back wall and the back section is notcoated with ceramic.

In a further embodiment there is provided a burner wherein the upperfront wall continues to the upper back wall and the back section iscoated with ceramic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway isometric view of one embodiment of a burneraccording to the present disclosure having a descending baffle.

FIG. 2 is a cutaway side view through the burner of FIG. 1.

FIG. 3 is a cutaway isometric view one embodiment of a burner accordingto the present disclosure having an ascending baffle

FIG. 4 is a cutaway side view through the burner of FIG. 3.

FIG. 5 is a cutaway side view of a burner having both a descendingbaffle from the top of the upper section and a baffle extending from thetop wall of the lower flow passage.

FIG. 6 is a cutaway isometric view of the burner of FIG. 5.

FIG. 7 is a cutaway isometric view of a wall burner typically used inpyrolysis furnaces.

FIG. 8 is a cutaway isometric view of a wall burner typically used inpyrolysis furnaces but with design elements in accordance with thepresent disclosure.

FIG. 9 is schematic drawing of an example ethylene furnace in which aburner designed in accordance with the present disclosure could beinstalled.

FIG. 10 is an isometric view of a floor burner designed in accordancewith the present disclosure displaying shading representing theoperating surface temperature of the burner constructed of metal.

DETAILED DESCRIPTION

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, etc. used in the specification and claims are to beunderstood as modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that can vary depending upon the properties that theembodiments disclosed herein desire to obtain. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10; that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10. Because the disclosednumerical ranges are continuous, they include every value between theminimum and maximum values. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations.

All compositional ranges expressed herein are limited in total to and donot exceed 100 percent (volume percent or weight percent) in practice.Where multiple components can be present in a composition, the sum ofthe maximum amounts of each component can exceed 100 percent, with theunderstanding that, and as those skilled in the art readily understand,that the amounts of the components actually used will conform to themaximum of 100 percent.

As used in this specification substantially metal or substantiallymetallic and metallic all mean, relative to the total construction ofthe burner not less than 80% of the burner is metallic and the balanceis an optional ceramic over coating on limited external surfaces of theburner as described below. In other words, the burner has no more than20 wt. % of ceramic or refractory, or no more than 10 wt. % or no morethan 5 wt. %, of ceramic or refractory.

In some embodiments, the substantially metallic burner disclosed hereinis characterized by having a substantially metallic flow passage or pathfor one or more gaseous oxidants, for example air, but possibly oxygenenriched air, or a mixture of oxygen and an inert gas (other thannitrogen), defined by at least one wall (e.g. tubular) wherein theinterior surface of the wall comprises a series of parallel longitudinalinternal ribs or channels to direct the flow of at least a gaseousoxidant, for example air, over the internal surface of saidsubstantially metallic flow passage. There is a balance between theconvective cooling of the fuel and oxidant flowing through the burnerrelative to the heat release of the combusting fuel. The convectivecooling flow rate is interdependent with the heat release rate, fuelcomposition and typical excess air, which results in a wet molarconcentration of oxygen between 1% and 10%. The required heat release ofthe burner and the flow rate of oxidant and fuel will define the rangeof sizes of the burner. This range will be further defined by the rangeof velocities of oxidant and fuel velocities required for cooling. Andthe maximum practical pressure drop of the fuel and oxidant as it flowsthrough the burner. The flow rate of fuel and oxidant can be calculatedas needed by a person of ordinary skill in the art. The remaining partsof the burner are metallic, provided however, that portions of theburner adjacent, above (e.g. heat shield) or below the flame may have acomplete or partial refractory coating. In some embodiments thelongitudinal channels have a height to width ratio from 0.1 to 2 in someembodiments from 0.5 to 2, in some embodiments from 0.5 to 1. The ribsmay have a height from 4 to 25 mm, or from 8 to 22 mm, in some instancesfrom 10 to 20 mm. The ribs or channels may cover from about 15 to 100%,in some embodiments from 25 to 100%, in some embodiments from 60 to 100%of the internal surface area of the flow path. When the ribs or channelscover less than 100% of the internal surface area of the flow path theribs or channels form a continuous series of parallel ribs or channelsat least on the internal surface of the portions of the burner exposedto the cracking furnace.

The metallic walls may have a thickness from 4 to 25 mm, or from 8 to 22mm, in some instances from 10 to 20 mm.

The channels may be replaced with longitudinal fins or protuberances.

The fins may have dimensions and spacing comparable to the longitudinalchannels. They may have a height form about 4 to 25 mm, or from 8 to 22mm, in some instances form 10 to 20 mm and a thickness from 2 to 20 mm,in some embodiments from 5 to 15 cm and be spaced apart 2 mm to 2 cm, insome instances from 5 mm to 1.5 cm.

The fins may have a number of cross sectional shapes, such asrectangular, square, triangular or trapezoidal. A trapezoidal shape maynot be entirely intentional, but may arise from the manufacturingprocess, for example when it is too difficult or costly to manufacture(e.g. cast or machine) a triangular cross section.

In some embodiments the fin may be cast as part of the metal surface orbe welded to the metal surface.

The protuberances are closed solids.

The protuberance may have geometrical shape, having a relatively largeexternal surface that contains a relatively small volume, such as forexample tetrahedrons, pyramids, cubes, cones, a section through a sphere(e.g. hemispherical or less), a section through an ellipsoid, a sectionthrough a deformed ellipsoid (e.g. a tear drop) etc. Some useful shapesfor a protuberance include:

-   -   a tetrahedron (pyramid with a triangular base and 3 faces that        are equilateral triangles);    -   a Johnson square pyramid (pyramid with a square base and sides        which are equilateral triangles);    -   a pyramid with 4 isosceles triangle sides;    -   a pyramid with isosceles triangle sides (e.g. if it is a four        faced pyramid the base may not be a square it could be a        rectangle or a parallelogram);    -   a section of a sphere (e.g. a hemi sphere or less);    -   a section of an ellipsoid (e.g. a section through the shape or        volume formed when an ellipse is rotated through its major or        minor axis);    -   a section of a tear drop (e.g. a section through the shape or        volume formed when a non uniformly deformed ellipsoid is rotated        along the axis of deformation); and    -   a section of a parabola (e.g. section though the shape or volume        formed when a parabola is rotated about its major axis—a        deformed hemi- (or less) sphere), such as e.g. different types        of delta-wings.

The spacing and height of the protuberances is comparable to that forfins. They may have a height form about 4 to 25 mm, or from 8 to 22 mm,in some instances form 10 to 20 mm and a thickness from 2 to 20 mm, insome embodiments from 5 to 15 cm and be spaced apart 2 mm to 2 cm, insome instances from 5 mm to 1.5 cm.

The protuberances may also be cast on to the internal surface of themetal. In some embodiments the protuberances form an array. In someembodiments the array is symmetrical, for example they may be inparallel rows (linear array) or with the protuberances in adjacent rowsoffset by the array spacing (diamond type array)

The density of the cooling channels, fins, protuberances or combinationsthereof means the number of channels fins or array of protuberances perunit length transverse to the channels fins or array of protuberances(e.g. 5 channels per cm.) in those areas where the channels are present.This is distinct from the surface area coverage of the cooling channels.For example if only half of the internal surface of the metal componenthas cooling channels fins or protuberances, the channels fins orprotuberances would have a different dimension than for channelscovering the entire surface of the metal component. The fabricationcosts for these different designs would differ so that in someembodiments the channel, fin, protuberance or protuberance array designor combinations thereof and surface coverage (either total or segregatedby the type of heat conductive structure) is optimized to reducemanufacturing cost.

The channels, fins, protuberances or combinations thereof may cover fromabout 15 to 100%, in some embodiments from 25 to 100%, in someembodiments from 60 to 100% of the internal surface area of the flowpath. When the ribs or channels cover less than 100% of the internalsurface area of the flow path the ribs or channels form a continuousseries of parallel ribs or channels at least on the internal surface ofthe portions of the burner exposed to the cracking furnace.

The burner additionally comprises a metallic fuel line which terminatesproximate the external front surface of the burner at from 25 to 75%, orfrom 40 to 65% of the height of the front of the flow passage.

One embodiment of the present disclosure having only a descending bafflewill now be described in conjunctions with FIGS. 1 and 2 in which likeparts have like numbers.

In FIGS. 1 and 2, the burner comprises a lower flow channel for one ormore gaseous oxidants, 1 having an open back or upstream end. The flowchannel is defined by a two equal length closed side walls 2 (only oneis shown), a closed bottom wall 3 which extends beyond closed top wall 4and a front wall 5. The top wall 4 does not extend as far as the sidewalls 2. As a result the lower flow channel defines an upward facingvent 6. In the embodiment shown there is a curved section 7 whichcooperates with the top wall and defines the upward vent 6. However oneskilled in the art would recognize the curved section 7 while desirableis not essential and the upper wall could extend further forward tostill define the vent 6.

The burner also comprise an upper metal section or duct. The uppersection comprises two side walls 8, a back wall 9 and a front wall 10which cooperates with vent 6 to provide a continuous passage way. Thereare one or more holes in the curved section 7 or back wall 9, and thefront wall 10 at substantially the same height (as used hereinsubstantially the same height means a variation in height that is lessthan 10%, or for example less than 5%, or less than 2%) and lateraldisplacement from the side walls to permit the passage of one or moremetallic fuel supply lines 11 through the burner.

At the top of the upper metal section are one or more top plates 12.There is a front top plate 12. While the figures show a flat top plateit may optionally have a rounded leading edge. There are one or moreoptional circular passages 13 through the leading edge of the top plate.While circular passages 13 are shown in the figure they are notessential to the operation of the burner. The top plates 12 cooperate todefine one or more openings 14 at the top of the upper section or duct.The openings may be may be circular, oval, or polygon (e.g. triangular,rectangular or square). As used herein substantially circular meanscircular, oval, or polygon (e.g. triangular, rectangular or square).

In the embodiment shown in FIGS. 1 and 2 there is a hanger 15 whichsupports the top plates and also supports a descending baffle 16. Thehanger is positioned so that the descending baffle 16 is not more than10% forward of the trailing edge of the leading top plate 12. The baffledescents inside the upper metal section or duct of the burner from 10 to50%, or from 15 to 30% of the height of the front wall 10 of saidburner; and extends laterally across the inner surface of the burnerfrom 100 to 75% of the width of the face of said burner, provided thatif the baffle does not extend across 100% of the inner surface of theburner it is positioned so that there are substantially equal openings(as used herein substantially equal openings means a variation in heightthat is less than 10%, or for example less than 5%, or less than 2%) oneach side of the baffle relative to the side walls of the metal uppersection. If the baffle extends far enough into the top metal section ofthe burner there may be holes in the baffle to permit a fuel supply lineto run through the baffle. If present the openings at the side of thebaffle permit a swirling of the oxidant, for example air, flowingthrough the upper metal section of the burner. It is believed thisswirling promotes good mixing of the fuel and the oxidant reducing NOxemissions.

Optionally, the walls of the front of the burner exposed to the interiorof the furnace (e.g. front walls 5 and 10) have ribs or channels asdescribed above. Additionally the front face of the baffle 16 mayoptionally also have ribs. Other internal surfaces of the burner couldalso have ribs or channels.

FIGS. 3 and 4 illustrate an embodiment having an ascending baffle. InFIGS. 3 and 4 like parts have like numbers.

In FIGS. 3 and 4, the burner comprises a lower flow channel 21 having anopen back or upstream end. The flow channel is defined by a two equallength closed side walls 22 (only one is shown), a closed bottom wall 23which extends beyond closed top wall 24 and a front wall 25. The topwall does not extend as far as the side walls. As a result the lowerflow channel defines an upward facing vent 26.

The burner also comprise an upper metal section or duct. The uppersection comprises two side walls 27 (only one is shown), a back wall 28and a front wall 29 which cooperates with vent 26 to provide acontinuous passage way. There are one or more holes 30 in the back wall28 and the front wall 29 at substantially the same height and lateraldisplacement from the side walls to permit the passage of one or moremetal fuel supply lines not shown through the burner.

At the top of the upper metal section are supporting flanges 31 and 32which support one or more top plates 33. There is a front top plate 33which is shown as flat but optionally it may have a rounded leadingedge. Optionally, there are one or more circular passages 34 through theleading edge of the top plate. These holes 34 are optional and need notbe present in the burner. The top plates 33 cooperate to define one ormore openings 35 at the top of the upper section or duct. The openingsmay be may be circular, oval, or polygon (e.g. triangular, rectangularor square).

In the embodiment show in FIGS. 3 and 4 there is baffle 37 which extendsfrom top wall 24 of the flow channel 21. The baffle 37 curves up intothe upper metal section (duct) of the burner from about 15 to 75% of theheight of the upper metal section. In this embodiment, the baffle 37 maycompletely traverses the upper metal or duct section. As shown in FIG.4. If the baffle extends sufficiently high in the upper metal section ofthe burner there are one or more holes 36 in the baffle 37 to permit ametal fuel supply line to pass through the baffle 37.

The opening at the top of the baffle permits a swirling of the oxidant,for example air, flowing through the upper metal section of the burner.It is believed this swirling promotes good mixing of the fuel and theoxidant reducing NOx emissions.

In the embodiment shown in FIGS. 3 and 4 the walls of the front of theburner exposed to the interior of the furnace (e.g. front walls 25 and29) have ribs or channels 38 as described above. Additionally the frontface of the baffle 37 may also have ribs. Other internal surfaces of theburner could also have ribs or channels.

FIGS. 5 and 6 show an embodiment of the metallic burner having both adescending and ascending baffles. Without wishing to be bound by theoryit is believed that the narrowing the flow passage increases flowvelocity and, therefore, increase heat transfer to portions of theburner exposed to the cracking furnace.

In FIGS. 5 and 6, the burner comprises a lower flow channel 41 having anopen back or upstream end. The flow channel is defined by a two equallength closed side walls 42 (only one is shown), a closed bottom wall 43which extends beyond top wall 44 and a front wall 45. The top wall 44does not extend as far as the side walls 42. As a result the lower flowchannel defines an upward facing vent 46.

The burner also comprise an upper metal section or duct. The uppersection comprises two side walls 47 (only one is shown), a back wall 48and an extension of the front wall 49 which cooperates with vent 46 toprovide a continuous passage way. There are one or more holes 50 in theback wall 48 and the front wall extension 49 at substantially the sameheight and lateral displacement from the side walls to permit thepassage of one or more metal fuel supply lines not shown through theburner.

In the embodiment shown the front wall further extends up through afront section 54 which may optionally be rounded and through a flat backsection 53 until it joins with the back wall 48. In the flat backsection there are series of apertures (openings which may be may becircular, oval, or polygon (e.g. triangular, rectangular or square)) 55.Depending from the sides of the flat sections are a duct elements 52which direct the flow of oxidant through the apertures 55. In theembodiment shown there are a number of holes 59 through the frontsection 54. However the holes are optional and need not be present.

Also, dependent from the leading edge of apertures 55 is structuralelement 51 which helps support hangar 56 for the baffle 57 and alsostabilized duct element 54.

The hanger is positioned so that the descending baffle 57 is not morethan 10% forward of the leading edge of the aperture 55. The operationof baffle 57 is as described relative to FIGS. 1 and 2.

In the embodiment shown in FIGS. 5 and 6 there is also baffle 58, whichextends upward from top wall 44 of the flow channel 41. The baffle 58curves up into the upper metal section (duct) of the burner from about15 to 75, or from about 30 to 55% of the height of the upper metalsection. In this embodiment, the baffle 58 may completely traverses theupper metal or duct section (e.g. from 100 to 75% of the width of theburner as described above). If the baffle 58 extends sufficiently highin the upper metal section (duct) of the burner there may be one or moreholes in the baffle to permit one or more metal fuel supply line to passthrough the baffle 58.

The tubular burners as described above may be mounted in the wall of thefurnace and the burners as shown in the figures may be floor mounted.The refractory lining in the wall or floor, as the case may be, has anopening through which the burner fits and then a refractory and cementare used to close the opening through which the burner was fitted. Theburner is also attached to the external supports (frame) for the furnaceand the external ducts to supply oxidant, for example air, to theburner. Also the fuel supply lines are connected to the fuel supply, forexample, natural gas.

In a similar manner, one can design a wall burner wherein the refractorytile surrounding the wall burner is replaced by a metal box or platewith a flow channel to direct oxidant along the internal surface of themetal portion whose external portion is exposed to the high temperaturesof the furnace.

FIG. 7 shows a sectioned view of a wall burner typical of a pyrolysisfurnace. FIG. 7 is meant to show the concepts of a typical wall burnerbut does not show all details. The wall burner 101, is used to directfuel and oxidant into the furnace for combustion. Fuel is injected intothe wall burner through an inlet orifice 106 where it mixes with airfrom the primary air duct 104. The primary air duct is formed through anannular opening around the wall burner 101 and muffler 109. The muffleris used to reduce combustion noise. Premixed fuel flows through theburner and enters the furnace through a series of guide vanes 107.Secondary air enters the furnace through an opening between the wallburner 101 and refractory tile 108 (not shown is a door or means tocontrol the amount of secondary air). The secondary air flow makes upthe remainder of the oxidants required to fully combust the fuel.Combustion occurs in part on the refractory tile 108 surrounding thewall burner 107 and therefore is expected to have high surfacetemperatures. The wall burner 101 and refractor tile 108 are mountedbetween the furnace interior wall 102 and furnace exterior wall 103. Thefurnace walls, defined as the surfaces 102 and 103 and the space betweenthem are constructed from a variety of metal and refractory materials.

FIG. 8 shows a sectioned view of a wall burner typical of a pyrolysisfurnace with design elements in accordance with the ideas of the presentdisclosure. FIG. 8 is meant to show the concepts of a typical wallburner but does not show all details. This burner assembly has beenmodified to remove all refractory materials. The wall burner 151, isused to direct fuel and oxidant into the furnace for combustion. Fuel isinjected into the wall burner through an inlet orifice 156 where itmixes with air from the primary air duct 154. The primary air duct isformed through an annular open around the wall burner 151 and muffler159. The muffler is used to reduce combustion noise. Premixed fuel flowsthrough the burner and enter the furnace through a series of guide vanes157. Secondary air enters the furnace through an opening between themetal tile 158 and the secondary air guide 160 (not shown is a door ormeans to control the amount of secondary air). The guide 160 is used todirect secondary air flow over the surfaces of the metal tile exposed tothe high temperature environment in the radiant section of the crackingfurnace. The secondary air flow makes up the remainder of the oxidantsrequired to fully combust the fuel. Combustion occurs in part on themetal tile 158 surrounding the wall burner 151 and therefore is expectedto have high surface temperatures. The secondary air keeps the surfaceof the metal tile 158 below the distortional temperature. The wallburner 151 and metal tile 158 are mounted between the furnace interiorwall 152 and furnace exterior wall 153. The furnace walls, defined asthe surfaces 152 and 153 and the space between them are constructed froma variety of metal and refractory materials.

The metallic burners also comprise ancillary equipment such as pilotlights, and the fuel feed there for joining members for duct works andany mechanical oxidant flow controllers as well as instrumentation.

The refractory material may be any type of refractory materials that arecommonly used in the construction of a furnace refractory wall. Examplesof such refractory materials include dolomites, silicon carbide,aluminates (A1203), aluminum silicates, chromites, silica, alumina,zirconia (Zr02), and mixtures thereof. In some embodiments, suchrefractory materials are selected from silica, alumina (A1203), aluminumsilicates, zirconia, (Zr02), and mixtures thereof. Such a refractory mayoptionally be non-porous in nature, even though the mentioned refractorymaterials are typically porous. In some embodiments, the refractory willbe porous and have a porosity of not less than 0.1 cc/g. In someembodiments, the porosity may be from 0.1 to 0.5 cc/g, or from 0.1 to0.3 cc/g.

Examples of refractory walls include Empire (trademark) S, which is ahigh duty dry press fireclay brick, Clipper (trademark), Korundal XD(trademark) and Insblok-19 available from A.P. Green Industries, Inc.(of Mexico, Mo.). An example of a ceramic fiber refractory includesInsboard 2300 LD also available from A.P. Green Industries, Inc. Theserefractory materials contains approximately 9.7% to 61.5% silica (SiO₂),12.1% to 90.0% alumina (Al₂O₃), 0.2% to 1.7% iron oxide (Fe₂O₃), up to27.7% lime (CaO), 0.1% to 0.4% magnesia (MgO), 2.0% to 6.3% titania(TiO₂) and 0.1% to 2.4% of alkalies (Na₂O plus K₂O).

The refractory use to coat the top plates may have a similarcompositions.

Cracking furnaces operate with walls at temperatures from about 700° C.to about 1350° C., or from about 850° C. to about 1200° C., or from 850°C. to 1100° C.

The metallic components used in the burner should be mechanically stableat such temperatures. The metal components may be made from any hightemperature steel such as stainless steel selected from wroughtstainless, austenitic stainless steel and HP, HT, HU, HW and HXstainless steel, heat resistant steel, and nickel based alloys. The coilpass may be a high strength low alloy steel (HSLA); high strengthstructural steel or ultra high strength steel. The classification andcomposition of such steels are known to those skilled in the art.

In one embodiment the stainless steel, for example heat resistantstainless steel, in some embodiments comprises from 13 to 50, or from 20to 50, or from 20 to 38 weight % of chromium. The stainless steel mayfurther comprise from 20 to 50, or from 25 to 50, or from 25 to 48, orfrom about 30 to 45 weight % of Ni. The balance of the stainless steelmay be substantially iron.

Embodiments disclosed herein may also be used with nickel and/or cobaltbased extreme austentic high temperature alloys (HTAs). In someembodiments the alloys comprise a major amount of nickel or cobalt. Insome embodiments the high temperature nickel based alloys comprise fromabout 50 to 70, or from about 55 to 65 weight % of Ni; from about 20 to10 weight % of Cr; from about 20 to 10 weight % of Co; and from about 5to 9 weight % of Fe and the balance one or more of the trace elementsnoted below to bring the composition up to 100 weight %. In someembodiments the high temperature cobalt based alloys comprise from 40 to65 weight % of Co; from 15 to 20 weight % of Cr; from 20 to 13 weight %of Ni; less than 4 weight % of Fe and the balance one or more traceelements as set out below and up to 20 weight % of W. The sum of thecomponents adding up to 100 weight %.

In some embodiments the steel may further comprise a number of traceelements including at least 0.2 weight %, up to 3 weight %, or forexample, 1.0 weight %, up to 2.5 weight %, or for example, not more than2 weight % of manganese; from 0.3 to 2, or from 0.8 to 1.6, or forexample less than 1.9 weight % of Si; less than 3, or for example lessthan 2 weight % of titanium, niobium (for example less than 2.0, or lessthan 1.5 weight % of niobium) and all other trace metals; and carbon inan amount of less than 2.0 weight %. The trace elements are present inamounts so that the composition of the steel totals 100 weight %.

One embodiment of the present disclosure is demonstrated in FIGS. 9 and10. FIG. 9 shows a simple schematic of a Foster-Wheeler pyrolysisfurnace that can be used for cracking ethane to ethylene. In a crackersuch as the ethylene cracker shown in FIG. 9, the feed stock 201 (amixture of ethane and steam) enters a coil 202 passing through theexhaust portion of the 203 typically referred to as the convectionsection of the furnace. The feed is pre-heated in the convection sectionto a controlled and specific temperature. In some embodiments, steam isalso heated in the convection section in a separate coil 207. In someembodiments, boiler feed water is also heated in the convection sectionin a separate coil 206. The coil 202 with the feed stock 201 passesthrough the radiant section 204 of the furnace before it exits 205 atwhich point it may be rapidly quenched to a lower temperature. The coil202 passes through the radiant section of the furnace 204 where it isexposed to the heat generated by the burners 208. The furnace shown inFIG. 9 displays a cracking furnace configuration with two radiantsections with the coil passing through both radiant sections. There arenumerous other configurations including a furnace with a single radiantsection.

Computational fluid dynamics (CFD) has been used previously to model theoperation of the radiant section of a NOVA Chemicals ethane cracker.Some embodiments of operation of this section of this particularpyrolysis furnace have pre-heated combustion air at 215° C. air and fuelcomposed of a mixture of 60% molar fraction hydrogen and 40% molarfraction natural gas at a pre-heated temperature of 130° C. The burnerswithin the furnace are commercially available low-NOX burnersconstructed of refractory typically used in high temperature furnaces.The single burner heat release rate is approximately 5 MMBtu/hr (1.5 MW)with the flue gas wet oxygen molar concentration at 2%. Real plant dataand CFD model results have been compared, including but not limited tothe surface temperature of the process coils, surface temperature of therefractory burners, flue gas exit temperature and process coil heattransfer rates. A comparison of the modeled vs. plant operatingmeasurements was found to be sufficiently close (within 10%) such thatit could be used for the prediction of plant performance in a practicalmanner.

This validation work was used to define model requirements and settingsto predict the performance of a burner designed using metal as amaterial of construction instead of refractory material in accordancewith the present disclosure. FIG. 9 shows a profile view of aFoster-Wheeler style pyrolysis furnace with the radiant section 204 andthe locations of burners 208. FIG. 10 shows the surface temperature aspredicted by NOVA Chemicals CFD of a burner (such as shown in FIG. 5)designed in accordance with this disclosure and operating at conditionsas described in the paragraph above. The temperature scale has a rangeselected to show temperatures between 500° C. and 1000° C. Temperaturesbelow or above this range are shown at the extremes of the scale. FIG.10 shows that, for this example burner, the surface temperature is nohigher than 900° C., which is below the distortion temperature of metalsthat would be used for burner construction. This shows that there is abalance of heat transfer between the firing rate of the burner and theinternal cooling rate induced by the combustion air and the design ofthe metal burner.

What is claimed is:
 1. A substantially metallic burner having a servicetemperature of not less than about 1200° C. for a cracking furnaceoperating with walls at temperatures from 700° C. to 1350° C.comprising: i) a substantially metallic flow passage defined by at leastone surface having a downstream outlet and at least one upstream inletfor at least a gaseous oxidant; ii) said substantially metallic flowpassage having at least one baffle directing the flow of oxidant andfuel against the internal surface of the burner facing the furnace; andiii) optionally one or more arrays of heat convective surfaces selectedfrom baffles ribs, fins and protuberances to direct the flow of said atleast a gaseous oxidant over said one or more arrays on the internalsurface of said substantially metallic flow passage.
 2. The burneraccording to claim 1, having an arrays of heat convective surfaces thatare ribs that define at least one continuous series of parallel channelsat least on the internal surface of the portions of the burner exposedto the cracking furnace.
 3. The burner according to claim 2, wherein thechannels have a height to width ratio from 0.1 to
 2. 4. The burneraccording to claim 3, wherein the metallic fuel line terminatesproximate the external front surface for said flow passage from 25 to75% of the height of the front of the flow passage.
 5. The burneraccording to claim 4, wherein said at least one metallic surface has athickness from 4 to 25 mm.
 6. The burner according to claim 5,comprising in cooperating arrangement: i) a lower metal flow passage forone or more gaseous oxidants having an open back end, closed side wallsand a closed bottom wall, a front wall and a top wall which does notextend the full length of the side walls to define an open upward facingvent in the upper front end of the flow passage; and a metal front wallcontinuous with the bottom wall of the flow passage; ii) a metal uppersection having the same width as the metal flow passage comprising afront wall, two parallel side walls and a rear wall defining a chamber,an open bottom which co-operates with the open vent in the flow passageand a front wall and an open top said front wall and back wall havingopenings therein at substantially the same height and lateraldisplacement to provide for one or more fuel supply lines passing fromthe back to the front of said upper section; iii) either: a) one or moremetal, or ceramic coated metal, top plates cooperating with the open topof the upper metal section, said one or more top plates having asubstantially planar surface and optionally having a curved leading edgeand one or more substantially circular passageways there through, theback section having one or more polygon outlets for said one or moregaseous oxidant there through; or b) a continuation of the upper frontwall extending to the back wall of the upper section said continuationhaving a leading edge optionally curved and optionally having one ormore substantially circular passageways there through, and asubstantially planar back section having one or more polygon outlets forthe oxidant there through, said back section optionally being coatedwith a ceramic; and iv) one or more baffles extending into said metalupper section.
 7. The burner according to claim 6, wherein a descendingbaffle depending from a region not more than 10% forward of the forwardlip of said one or more outlets for said one or more gaseous oxidants,to the forward lip of said one or more outlets for said one or moregaseous oxidants, said descending baffle descending inside the uppermetal section of the burner from 50 to 90% of the height of the frontface of said burner; and extending laterally across the inner surface ofthe burner from 100 to 75% of the width of the face of said burner, saiddescending baffle being positioned so that there are substantially equalopenings on each side of the descending baffle relative to the sidewalls of the metal upper section and where necessary said descendingbaffle having one or more circular channels there through to permit oneor more fuel supply lines to pass there through.
 8. The burner accordingto claim 7, having series of parallel longitudinal internal ribs todirect the flow of said at least a gaseous oxidant over the forwardfacing surface of said descending baffle.
 9. The burner according toclaim 8, further comprising an ascending baffle extending forward fromthe upper wall of said lower metal flow passage into from 45 to 85% ofthe open area in the chamber of a metal upper section.
 10. The burneraccording to claim 9, wherein said ascending baffle extending forwardfrom the upper wall of said lower metal flow passage is bent in itsforward section up towards said one or more outlets to provide anupwards facing ascending baffle parallel to the inner front wall ofupper section and where required the upward extending section of saidascending baffle having one or more circular channels there through topermit one or more fuel supply lines to pass there through.
 11. Theburner according to claim 10, wherein said ascending baffle extendingforward from the upper wall of said lower metal flow passage furthercomprises on the surface facing the inner front wall of upper section aseries of parallel longitudinal internal ribs to direct the flow of saidat least a gaseous oxidant over the internal surface of saidsubstantially metallic flow passage.
 12. The burner according to claim11, wherein the channels have a height to width ratio from 0.1 to
 2. 13.The burner according to claim 5, comprising in cooperating arrangement:i) a lower metal flow passage for one or more gaseous oxidants having anopen back end, closed side walls and a closed bottom wall, a front walland a top wall which does not extend the full length of the side wallsto define an open upward facing vent in the upper front end of the flowpassage; and a metal front wall continuous with the bottom wall of theflow passage; ii) a metal upper section having the same width as themetal flow passage comprising a front wall, two parallel side walls anda rear wall defining a chamber, an open bottom which co-operates withthe open vent in the flow passage and a front wall and an open top saidfront wall and back wall having openings therein at substantially thesame height and lateral displacement to provide for one or more fuelsupply lines passing from the back to the front of said upper section;iii) either: a) one or more metal, or ceramic coated metal, top platescooperating with the open top of the upper metal section, said one ormore top plates having a substantially planar surface and optionallyhaving a curved leading edge and one or more substantially circularpassageways there through, the back section having one or more polygonoutlets for said one or more gaseous oxidant there through; or b) acontinuation of the upper front wall extending to the back wall of theupper section said continuation having a leading edge optionally curvedand optionally having one or more substantially circular passagewaysthere through, and a substantially planar back section having one ormore polygon outlets for the oxidant there through, said back sectionoptionally being coated with a ceramic; and iv) an ascending baffleextending forward from the upper wall of said lower metal flow passageinto from 45 to 85% of the open area in the chamber of a metal uppersection.
 14. The burner according to claim 13, wherein said ascendingbaffle extending forward from the upper wall of said lower metal flowpassage is bent in its forward section up towards said one or moreoutlets to provide an upwards facing ascending baffle parallel to theinner front wall of upper section and where required the upwardextending section of said ascending baffle having one or more circularchannels there through to permit one or more fuel supply lines to passthere through.
 15. The burner according to claim 14, wherein saidascending baffle extending forward from the upper wall of said lowermetal flow passage further comprises on the surface facing the innerfront wall of upper section a series of parallel longitudinal internalribs to direct the flow of said at least a gaseous oxidant over theinternal surface of said substantially metallic flow passage.
 16. Theburner according to claim 15, wherein the channels have a height towidth ratio from 0.1 to
 2. 17. The burner according to claim 7, whereinsaid one or more top plates is present and is metal.
 18. The burneraccording to claim 7, wherein said one or more top plates is present andis metal coated with ceramic.
 19. The burner according to claim 9,wherein said one or more top plates is present and is metal.
 20. Theburner according to claim 9, wherein said one or more top plates ispresent and is metal coated with a ceramic.
 21. The burner according toclaim 13, wherein said one or more top plates is present and is metal.22. The burner according to claim 13, wherein said one or more topplates is present and is metal coated with a ceramic.
 23. The burneraccording to claim 7, wherein the upper front wall continues to theupper back wall and the back section is not coated with ceramic.
 24. Theburner according to claim 7, wherein the upper front wall continues tothe upper back wall and the back section is coated with ceramic.
 25. Theburner according to claim 9, wherein the upper front wall continues tothe upper back wall and the back section is not coated with ceramic. 26.The burner according to claim 9, wherein the upper front wall continuesto the upper back wall and the back section is coated with ceramic. 27.The burner according to claim 13, wherein the upper front wall continuesto the upper back wall and the back section is not coated with ceramic.28. The burner according to claim 13, wherein the upper front wallcontinues to the upper back wall and the back section is coated withceramic.
 29. The burner according to claim 5, comprising in cooperatingarrangement an elongated tubular body, having an inlet for fuel, anannular primary air duct concentric with the tubular body, an exit fromthe tubular body comprising one or more guide vanes, a secondary airsource and a cooperating baffle concentric with the tubular bodycooperating with a cover plate exposed to the furnace so that air flowsover the guide and across the cover plate.